Researchers at Washington University School of Medicine in St. Louis have found a key difference in the brains of people with Alzheimer's disease and those who are cognitively normal but still have brain plaques that characterize this type of dementia.

A new study shows that having a high amount of beta amyloid or "plaques" in the brain associated with Alzheimer's disease may cause steeper memory decline in mentally healthy older people than does having the APOE ɛ4 allele, also associated with the disease.